GB1587689A - Circumferentially compressed piston ring assembly and method - Google Patents

Description

PATENT SPECIFICATION

( 21) ( 31) ( 33) ( 44) ( 51) Application No 21699/78 ( 22) Filed 23 M Convention Application No 801638 ( 32) Fili United States of America (US)

Complete Specification published 8 April 1981

INT CL 3 F 16 J 9/28 ( 11) lay 1978 ( 19) ed 31 May 1977 in ( 52) Index at acceptance \\Wf F 2 T 37 E 2 B ( 54) CIRCUMFERENTIALLY COMPRESSED PISTON RING ASSEMBLY AND METHOD ( 71) We, CHEMPRENE, INC, a corporation of Delaware, 11061 Walden Road, Alden, New York 14004, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

The present invention generally relates to sealing devices and methods and, more particularly, to improved sealing devices and methods which are especially adapted for sealing piston and cylinder assemblies and the like.

Piston ring and expander combinations have heretofore been employed as sealing devices in piston and cylinder assemblies used in a wide variety of applications In general, it has been found advantageous to manufacture these rings of one-piece, substantially rigid construction with a split therein so as to facilitate their installation in a groove in the piston in overlying relation with the expander.

Heretofore, many of these split piston rings have been composed of a wide variety of materials including synthetic resins and have been characterized by a so-called stepped joint construction; that is, one wherein the ring ends are stepped and overlay one another In accordance with previously employed techniques, these rings were manufactured with a gap or circumferential spacing in their pre-installed condition which was expected to close or substantially close when the ring was fully installed within the bore of the cylinder in overlying relation with the elastomeric expander in a groove in the piston.

Experience with these synthetic resin stepped joint piston ring and elastomer expanders, however, has indicated a higher failure rate than was originally anticipated.

In this regard, it was found that upon installation in the cylinder bore, a gap was present, resulting in nibbling or extrusion of the elastomeric expander into the gap and producing a failure of the seal assembly It is believed that this problem has been caused, at least in part, by frictional forces present between the expander and ring, when installed, which have prevented circumferential travel of the ring ends to the extent necessary to close or at least substantially close the gap 55 According to a first aspect of the present invention there is provided an assembly for sealing opposing, reciprocable surfaces comprising: a resilient expander adapted to be mounted circumferentially on a cylindrical 60 member and a circumferentially compressible split seal ring adapted to overlie the resilient expander and in use to contact sealingly a cylindrical wall surrounding the cylindrical member, the seal ring being made 65 of a circumferentially compressible synthetic material so that once installed within the confines of the said cylindrical wall the material of the ring is circumferentially compressed 70 Preferably the sealing assembly further includes a secondary resilient seal mounted along a split of said split seal ring Conveniently a split of said split seal ring is in the form of a stepped joint having pairs of 75 opposing radial extending surfaces and a pair of opposing axially facing surfaces and a radially and axially compressible secondary resilient seal member can be mounted along one of said pair of opposing axially facing 80 surfaces Alternatively a radially and axially compressible secondary resilient seal can be mounted with a detent of said seal ring, said detent being open along a circumferential fate of the seal ring 85 Included within the scope of the present invention is the sealing assembly mounted in a cylindrical groove of a piston which is slidably movable with respective to a cylinder so that the split seal ring is in overlying 90 circumferential communication with said resilient expander and is circumferentially compressed whereby an outer circumferential surface of said seal ring is in slidable, sealing communication with said cylinder 95 According to a second aspect of the present invention there is provided a method for sealing opposing, reciprocable surfaces, comprising: selecting a split seal ring made of a circumferentially compressible synthetic 100 1587689 1,587,689 material; mounting said seal ring circumferentially over a resilient expander placed around a piston member; circumferentially compressing the material of the seal ring; and feeding the piston member, the resilient expander and the compressed seal ring into a cylinder member whose inner surface is adapted for opposing, reciprocating action with the piston member; such that once installed in the cylinder member the material of the seal ring is circumferentially compressed and a split in the split seal ring is substantially closed circumferentially Preferably said compressing step includes circumferentially and radially compressing said resilient expander member The method can further comprise the step of inserting a secondary resilient seal expander metnber between opposing surfaces at a split of said split seal ring.

Particular embodiments of the present invention will now be described by way of example with reference to the accompanying drawings; wherein:Figure 1 is an exploded perspective view of a first embodiment of sealing assembly including a stepped joint ring, before installation; Fig 2 is an elevational view of the embodiment of Fig 1, shown installed in a circumferential groove of a piston positioned within a circular cylinder shown in crosssection; Fig 3 is an enlarged fragmentary elevational view of the stepped joint ring of Fig 1; Fig 4 is an enlarged fragmentary elevational view of the stepped joint ring of Fig 2; Fig 5 is a horizontal sectional view of the installed seal assembly depicted in Figs 2 and 4, taken along line V-V of Fig 4; Fig 6 is a fragmentary elevational view of a second embodiment of stepped joint ring, depicted prior to installation; Fig 7 is a fragmentary elevational view of a seal assembly incorporating the stepped joint ring of Fig 6, shown as installed; Fig 8 is a horizontal sectional view of the seal assembly taken along the line VIIIVIII of Fig 7; Fig 9 is a fragmentary elevational view of a third embodiment of stepped joint ring, depicted prior to installation; Fig 10 is a fragmentary elevational view of a seal assembly, showing the ring of Fig 9 after installation; Fig 11 is a horizontal view, partly in plan and partly in section, showing parts of the end gap seal construction of Fig 10 with portions thereof broken away; Fig 12 is a fragmentary elevational view of a further embodiment, showing a further embodiment of the stepped joint ring after installation; Fig 13 is a horizontal sectional view of the seal assembly of Fig 12, taken along the line XIII-XIII of Fig 12; Fig 14 is a horizontal sectional view of one other embodiment of the seal assembly after it has been installed; and Fig 15 is a vertical sectional view of the 70 seal assembly of Fig 14, taken along the line XV-XV.

In the following description, and in the figures, like reference numerals indicate corresponding parts throughout the various 75 embodiments.

Referring firstly to Fig 1, a sealing assembly, generally referred to by reference numeral 21 includes a resilient expander 22, which may be of oval cross-section, and a 80 circumferentially compressible one-piece split seal ring having an oversized closed gap condition, which ring is generally referred to by reference numeral 23 Also shown is a cylindrical piston 24, having one or more 85 cylindrical grooves 25 Seal ring 23 includes overlapping ends forming a stepped joint, generally referred to by reference numeral 26 Stepped joint 26 includes opposing axially, radially extending surfaces 31,32 and 90 33,34.

Prior to the installation, as depicted in Fig.

1, gaps 35 and 36 may be present between opposing radial surfaces 31,32 and 33,34, respectively Gaps 35 and 36 may be between 95 0 to 0 010 inch, measured approximately along the circumference or ring 23, per inch of diameter of the ring 23 In any event, gaps and 36 if present are sized such that ring 23 is manufactured with an oversized closed 100 gap condition to insure that the gaps 35 and 36 will be substantially eliminated and at least one of the opposing radial surface pairs 31,32 and 33,34 is in mating engagement even after ring 23 has been installed and 105 circumferentially compressed while in overlying, frictional relationship with expander 22 Throughout the present specification a ring with an "oversized closed gap condition" is a ring wherein prior to installation in 110 a cylinder bore, the ring ends are in contact with each other, or at least in very close spatial relationship with each other so that installation of the ring within the bore of a cylinder is accommodated by reason of the 115 compression of the ring itself.

As shown in Fig 2, when assembly 21 is installed, gaps 35 and 36, if present prior to installation, are substantially eliminated, and at least one of the opposing radial surface 120 pairs 31, 32 and 33, 34 is in mating engagement The seal ring 23 is itself compressed circumferentially Fig 2 depicts sealing assemblies installed within grooves of piston 24 which is positioned for reciprocating move 125 ment within a cylinder 37, having a wall 38.

Fig 3 illustrates the stepped joint 26 of ring 23 having substantially no gaps prior to installation of the sealing assembly 21 Fig 4 shows that same assembly after it is installed 130 1,587,689 on piston 24 and within cylinder 37 (Fig 2).

In this embodiment, the stepped joint 26 has its axial surfaces in substantial mating engagement with no gap therebetween From Fig 5, the overlying engagement, which is an abutting, circumferential engagement, between the resilient expander 22 and the circumferentially compressible seal ring 23, both after installation, is depicted From this it can be seen that resilient expander 22 provides radial forces against the internal circumference of the circumferentially compressed seal ring 23, which force is transmitted through ring 23 to enhance the sealing engagement between sealing assembly 21 and cylinder wall 38 (Fig 2).

In Fig 6, a second embodiment of circumferentially compressible seal ring 23 is shown prior to installation A second resilient seal 41 is mounted along one of the pair of oppositely directed axial facing surfaces 42 or 43 Secondary seal 41 is constructed and positioned so that it will be compressed, upon installation, both radially and axially.

Fig 7 shows secondary resilient seal 41 in its compressed, installed state This compression insures that axial surfaces 42 and 43 are in mutal engagement, through secondary seal 41, in order to provide a securely fitting stepped joint relationship Compressed seal 41 also substantially fills the radial extent of the opening between axial surfaces 42 and 43 and can prevent the passage of any fluids which might seep between the closed gaps of the opposing radial surfaces 31, 32 and 33, 34 This arrangement, for practical purposes, eliminates leakage between the ring 23 and the pertinent sealed surface, for example, cylinder wall 38 (Fig 2) Fig 8 shows compressed seal 41 filling the radial extent axial surface 42 and axial surface 43 (Fig 7).

In Fig 9, a secondary resilient seal 41 a is located along stepped joint 26 within a detent 44 that is open along a radially extending edge of seal ring 23 a This provides a manner of mounting seal 41 a within a ring 23 a that is more easily molded than the ring 23 of, for example, the embodiment shown in Fig 6, wherein there are no apertures throughout the entire area of the axially extending circumferential surface of ring 23, which includes the surface area immediately adjacent secondary resilient seal 41 Figs 10 and 11 further illustrate the configuration of the secondary resilient seal 41 a of the embodiment of Fig 9.

Figs 12 and 13 show yet a further configuration of a secondary resilient seal 41 b which has a generally cubic structure prior to installation Figures 12 and 13 depict the installed combination of ring 23 b, resilient insert 22, and the compressed secondary seal 41 b.

Figs 14 and 15 depict a further configuration of secondary resilient seal 41 c and ring 23 c Conical seal 41 c is received within a conical opening 45 along the ring 23 c This seal 41 c is shown only in its installed, compressed state.

In the various embodiments discussed 70 herein, resilient expander 22 is preferably constructed of a synthetic rubber, for example a nitrile rubber Other suitable elastomeric materials may be substituted.

The circumferentially compressible seal 75 ring 23 must be of appropriate elasticity so as to permit the ring 23 having the oversized closed gap condition to be both installed over the piston 24 or the like and also to be circumferentially compressed upon installa 80 tion into the cylinder 37 or the like This requires a material of the type discussed elsewhere herein having a modulus of elasticity and a heat deflection temperature within the ranges specified herein The preferred 85 material for ring 23 is a nylon (polyamide) material that is glass fiber filled at a level of about 30 % by weight, having a modulus of elasticity of about 1,300,000 pounds per square inch, and having a heat deflection 90 temperature of about 485 F at 264 psi Other suitable molded resins may be substituted for the preferred filled nylon, provided they meet the requirements contained herein.

The present method of sealing eliminates 95 or significantly reduces leakage between opposing, reciprocating surfaces The method includes providing a sealing surface supplying ring having an oversized closed gap condition in order to impart circumfer 100 ential and radial compressive forces along one of the reciprocating surfaces to provide a uniformly fitting seal, to improve sealing of the surfaces, and to significantly extend the life of the seal 105 More particularly, the method includes selecting a seal ring that exhibits an oversized closed gap condition to insure that there will be substantially no gaps in the sealing surface or the seal ring even after the ring has 110 been installed and circumferentially compressed over an underlying resilient expander member The preferred ring has a modulus of elasticity between 900,000 to 4,000,000 pounds per square inch, preferably between 115 1,000,000 to 3,000,000 pounds per square inch The preferred materials should also have a heat deflection temperature between 300 ' to 600 'F, preferably between 400 to 525 I Generally, these will be injection or 120 compression molded thermoplastic or thermoset synthetic resins, preferably of the selflubricating type Ring members of this type can be manufactured in an oversized closed gap condition and can be advantageously 125 circumferentially compressed in accordance with the method.

As previously mentioned, the preferred material for the ring member is a filled polyamide Examples of other suitable mate 130 1,587,689 rials include polysulfones, polyether sulfones polyphenylene sulfides, ethylene-tetrafluoroethylene, and polybutylene terephthalate Preferably these materials are selflubricating, are injection or compression molded, and include a suitable filler, such as glass fiber or carbon These materials generally have some self-lubricating properties without having to add special lubrication substances They may also have incorporated therein lubricants such as molybdenum disuIfide, teflon (Registered Trade Marks), or silicone oils so as to increase their selflubricating properties.

The method includes circumferentially compressing a ring having a sealing surface that is in overlying circumferential communication with a resilient expander member thereby to develop radial and circumferential expansive forces This circumferentially compressed sealing surface is usually provided by gradually compressing the synthetic resin seal ring member around the resilient expander member, which is itself thus radially and circumferentially compressed, while feeding the leading circumferential edge of the'ring member between the surfaces being sealed This step continues until all of the sealing surface is between the reciprocable surfaces being sealed.

By these steps, the generally circumferential forces applied to compress the seal ring member in conjunction with its oversized closed gap condition and the generally radial forces provided by the resilient expander member combine to ensure that the sealing member remains in a closed gap position so as to provide a slidable seal between opposing cylindrical surfaces, which seal remains substantially leakage-free during reciprocating movement of the cylindrical surfaces.

Most importantly, the resilient expander remains substantially undamaged because the seal ring installation eliminates any significant gaps in the ring which avoids nibbling or extrusion of the resilient, elastomeric expander member which will lead to eventual failure of the seal assembly.

As an optional step in the method, a secondary resilient expander member may be provided within a stepped joint of the seal ring member By this step, a secondary seal is formed in order to substantially eliminate any fluid leakage through the axial surfaces of the stepped joint Generally, without this optional step some minimal leakage can take place across the sealing surface When this optional step is included, such leakage is all but eliminated Depending upon variables such as the fluids being acted upon by the piston-and-cylinder assembly, reciprocation speeds, time, and temperature, leakage on the order of 10 cc per minute may be observed when this step of providing the secondary seal is omitted.

The seal assemblies and method of the present invention may be used in a variety of environments, but they are particularly adapted for use as a piston ring in an annular groove of a piston of piston and cylinder arrangements included in heavy duty hydraulically powered equipment and/or high pressure oil hydraulic application, such as for example, a back hose system of materials handling equipment.

Use of the present invention can thus overcome the problems and disadvantages of stepped joint piston ring and expander sealing devices discussed above by the elimination of a gap in which the elastomeric oval expander can extrude into or nibble on and, at the same time, by increasing circumferential pressure of the ring thereby substantially improving the effectiveness of the seal ring within the cylinder bore.

Claims (23)

WHAT WE CLAIM IS:-

1 An assembly for sealing opposing, reciprocable surfaces comprising; a resilient expander adapted to be mounted circumfer 90 entially on a cylindrical member and a circumferentially compressible split seal ring adapted to overlie the resilient expander and in use to contact sealingly a cylindrical wall surrounding the cylindrical member, the seal 95 ring being made of a circumferentially compressible synthetic material so that once installed within the confines of the said cylindrical wall the material of the ring is circumferentially compressed 100

2 An assembly according to claim 1 further including a secondary resilient seal mounted along a split of said split seal ring.

3 An assembly according to claim 1 or claim 2 wherein a split of said split seal ring 105 is in the form of a stepped joint having pairs of opposing radially extending surfaces and a pair of opposing axially facing surfaces.

4 An assembly according to claim 3 as appendant on claim 2 wherein a radially and 110 axially compressible secondary resilient seal member is mounted along one of said pair of opposing axially facing surfaces.

An assembly according to claim 3 as appendant on claim 2 wherein a radially and 115 axially compressible secondary resilient seal is mounted within a detent of said seal ring, said detent being open along a circumferential face of the seal ring.

6 An assembly according to any one of 120 the preceding claims wherein a split of said split seal ring in a relaxed state prior to installation is a gap of between 0 and 0 010 inch measured along a circumference of the ring, per inch of diameter of the ring 125

7 An assembly according to any one of the preceding claims wherein said seal ring has a modulus of elasticity within the range 900,000 to 4,000,000 pounds per square inch.

8 An assembly according to claim 7 130 1,587,689 wherein the modulus of elasticity of the seal ring is within the range 1,000,000 to 3,000,000 pounds per square inch.

9 An assembly according to any one of the preceding claims wherein said seal ring has a heat deflection temperature within the range 300 TF to 600 TF.

An assembly according to claim 9 wherein the heat deflection temperature of the seal ring is within the range 400 T to 525 TF.

11 An assembly according to any of the preceding claims wherein said seal ring is made of a material which is a synthetic resin having self-lubricating properties.

12 An assembly according to any one of claims 1 to 10 wherein said seal ring is made of a material which is a synthetic resin into which one or more lubricants are incorporated.

13 An assembly according to any one of the preceding claims wherein said seal ring is made of a material which is a filled synthetic resin.

14 An assembly according to any one of claims 11 to 13, wherein said synthetic resin is selected from polyamides, polysulfones, polyether sulfones, polyphenylene sulfides, ethylene-tetrafluoroethylene, and polybutylene terephthalate.

A sealing assembly according to any one of the preceding claims mounted in a cylindrical groove of a piston which is slidably movable with respect to a cylinder such that the split seal ring overlies said resilient expander and is circumferentially compressed whereby an outer circumferential surface of said seal ring is in slidable, sealing communication with said cylinder.

16 A method for sealing opposing, reciprocable surfaces, comprising: selecting a split seal ring made of a circumferentially compressibly synthetic material; mounting said seal ring circumferentially over a resilient expander place around a piston member; circumferentially compressing the material of the seal ring; and feeding the piston member, the resilient expander and the compressed seal ring into a cylinder member whose inner surface is adapted for opposing, reciprocating action with the piston member; such that once installed in the cylinder member the material of the seal ring is circumferentially compressed and a split in the split seal ring is substantially closed circumferentially.

17 A method according to claim 16 wherein said compressing step includes circumferentially and radially compressing said resilient expander member.

18 A method according to claim 16 or claim 17 further comprising using a seal ring that has a modulus of elasticity between 900,000 to 4,000,000 pounds per square inch and a heat deflection temperature between 3000 to 600 'F.

19 A method according to claim 18 further comprising using a seal ring that has a modulus of elasticity between 1,000,000 and 3,000,000 pounds per square inch and a heat deflection temperature between 400 to 525 TF.

A method according to any one of claims 16 to 19 further comprising the step of inserting a secondary resilient seal expander member between opposing surfaces at a split of said split seal ring.

21 A sealing assembly substantially as herein described with reference to Figs 1 to 5, Figs 6 to 8, Figs, 9 to 11, Figs, 12 to 13 or Figs 14 to 15 of the accompanying drawings.

22 A piston and sealing assembly according to claim 15 as herein described with reference to Figs 1, 2 and 4; Fig 7; Fig 10; Fig 12 or Figs 14 to 15 of the accompanying drawings.

23 A method according to claim 16 substantially as herein described.

Agents for the Applicants, MEWBURN ELLIS & CO, Chartered Patent Agents, and European Patent Attorney, 70/72 Chancery Lane, London WC 2 A l AD.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd -1981 Published at The Patent Office, Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.